The present invention relates to coating compositions adapted to enhance the adhesion of a coating or film to a substrate, a process for producing an adherent coating or film on a substrate and the resulting coated or laminated substrate. More particularly, this invention relates to a coating composition containing coupling agents plus adhesion enhancing ingredients, processes for preparing adherent polymeric coatings or films on substrates and photochromic articles.
Photochromic compounds exhibit a reversible change in color when exposed to light radiation involving ultraviolet rays, such as the ultraviolet radiation in sunlight or the light of a mercury lamp. Various classes of photochromic compounds have been synthesized and suggested for use in applications in which a sunlight-induced reversible color change or darkening is desired. The most frequently suggested classes of photochromic compounds are oxazines, pyrans, and fulgides.
It is reported that the outermost surface of most organic polymers is hydrophobic due to a preponderance of nonpolar groups and is, therefore, difficult to wet. Some polymers have such a low surface energy that it is difficult to formulate coatings that will wet the polymer surface. Many of the conventional coatings, e.g., protective hardcoats, paints, inks, and adhesives, applied to polymers are hydrophilic. Consequently, they do not form strong bonds with the hydrophobic surface of the polymer and, therefore, do not adhere well to the polymer.
Pretreatment processes are frequently used on polymeric substrates to increase the surface energy or wetting characteristics of the substrate and provide functional groups to interact with polar groups present in coatings or films applied to such substrates. Although methods exist for obtaining adhesion of coatings and films on various substrates, alternative methods are sought. There is a commercial need to produce adherent photochromic coatings and films on substrates in a rapid and economical manner.